This invention relates to bases for electron tubes, e.g. color picture tubes, and particularly to a base and an adapter therefor which permits simple conversion from one type of base to another type of base.
Certain types of electron tubes, e.g. color picture tubes, include a stem structure comprising a glass wafer, a circular array of stiff lead-in conductors sealed through the wafer, and a central opening through the wafer from which an exhaust tubulation extends. It is common practice to attach a base member, usually of some type of plastic material, over the lead-in conductors and exhaust tubulation. The base member serves to protect the lead-in conductors and the exhaust tubulation, and to provide an indexing means for insertion into a mating socket. Two types of bases which are commonly employed in the picture tube industry are those known as wafer bases and pin-protector bases.
Wafer bases, as employed in present day picture tubes, are disclosed, for example, in U.S. Pat. No. 2,498,378 issued to G. N. Phelps on Feb. 21, 1950 and in U.S. Pat. No. 3,278,886 issued to H. H. Blumenberg et al on Oct. 11, 1966. Such bases comprise a protector cup disposed over the exhaust tubulation of an electron tube stem, and a wafer flange which extends radially outwardly from the open end of the cup. The flange is abutted against the tube stem and is provided with an array of apertures through which the lead-in conductors of the stem are disposed. The Blumenberg et al patent additionally discloses a separate tubular silo extending from the flange alongside the cup for receiving one of the stem conductors thereon for high voltage insulation purposes. In these bases the lead-in conductors are spaced outwardly from the exhaust tubulation protector cup of the base, and are thus free-standing once they pass through the wafer flange of the base.
A pin-protector base, as employed in present-day picture tubes, is disclosed, for example, in U.S. Pat. No. 3,979,157 issued to L. J. Dimattio on Sept. 7, 1976. The pin-protector base is a modification of the wafer base in that the exhaust tubulation protective cup is provided with a plurality of longitudinal ribs along its outer cylindrical surface, and is enlarged so that the lead-in conductors lie protected in channel-like recesses of the base. The lead-in conductors of a pin-protector base are not free standing but instead lie in flush contact along the outer surface of the protector cup.
A manufacturer of electron tubes may wish to fabricate both wafer base tubes and pin-protector base tubes using the same tube processing equipment on his production line. To do so, processing sockets are provided which accommodate the larger pin-protector bases. When a tube having a wafer base is to be processed, an adapter is placed over the wafer base to convert it to a pin-protector base which can be properly received within the socket. Such an adapter is disclosed, for example, in U.S. Pat. No. 3,771,105 issued to E. Yamazaki et al on Nov. 6, 1973.
Where such adapters have been employed in the past, they have simply involved a suitable sleeve which is slipped over the wafer type base. In some instances the adapter sleeves are held on sufficiently snuggly by frictional engagement while at other times, due to a loose fit because of manufacturing tolerances, they fall off in normal handling of the tube along the production line. In the latter instances difficulties resulting in down time of the production line result.